Compressor unloading device



Patented Mar. 8, 1938 UNITED STATESl PATENT OFFICE Philip L. Crittenden, Edgewood, Pa., assignor to The Westinghouse Air Brake Company, Wilmerding, Pa., a corporation of Pennsylvania Application August 17,

19 Claims.

another spring and 4by the pressure of fluid com- Dressed by the compressor when the pressure of the fluid lubricant in a pressure system, including a pump drivenfrom the crank shaft of the compressor, increases suiiciently to overcome the force-of the first mentioned spring.

A similar operating mechanism for actuating the unloader valve is also disclosed and claimed in the copending application, now Patent 2,042,085 of Burton S. Aikman, issued May 26,

1936, and assigned to the assignee of the present application. The construction in both patents is subject to the disadvantage that upon failure or breakage of the spring effective to actuate the valve to unloading position, the compressor is not unloaded automatically but remains in loaded condition, 30 even though the compressor stops completely.

It is an object of this invention to obviate the above-mentioned diiiiculty and provide a construction and arrangementwhereby operation of the unloader valve to unload the compressor is effected positively by the pressure of the uid compressed by the compresser and without reliance on the integrity of a spring, whenever the speed of the compressor reduces below a certain speed.

40 It is another object of this invention to provide 'means for reducing the noise of operation of ai v 5 sectional casing including a crank case section 5 1934, Serial No. 740,212

enclosing a crank case chamber 6 and having an open end 'I, a cylinder or piston section 8, an end section 9 for closing the open end 1 of the crank case section 5, and an intake and discharge valve section II.

The wall of the crank case section 5 opposite the endopening 'I supports a horizontal tubular journal member I2, preferably integrally formed therein, which encloses a bearing chamber I3 having therein suitable anti-friction bearings., such as the ball bearings I4, for supporting a -rotatable crank shaft I5. The crank shaft I5 extends exteriorly of the journal member through an opening I6 in a closure member II that is secured to the end of the journal member and to casing Section5 by means of screws or bolts I8.

'Ihe compressor may be driven by any form of motor device, such as an electric motor or internal combustion engine, that is operatively connectedY to the exterior portion of the crank shaft I5-by` means of a. pulley wheel or gear wheel, a portion I9 of the hub of which is shown.

Any suitable means may be provided for sealing the opening I6 against fluid lubricant leakage therethrough, such as the packing ring gasket '2 I which is suitably supportedwithin a retainer 22 secured within the closure member. I'I. The packing ring gasket 2I is pressed radially inward against the exterior surface of hub portion I9 by a retaining spring-tensioned ring 23.

A trough or channel 24 secured to' or formed in the side wall of the crank case section 5 opens into the bearing chamber I3 through an opening 25 and fluid lubricant centrifugally thrown from the crank shaft is collected therein and conducted by gravitation into the bearing chamberv I3, from whence the fluid lubricant ows, 'past the ball bearings I4, back into' the crank ca se chamber 6.

The crank shaft I5 is provided with a counterbalanced crank arm 26 having a crank pin 21, to which is connected in the usual manner, a connecting rod 28 for operating a compressor piston 29 in the bore 3| of the piston section 8, so that as the crank shaft I5 is rotated, the piston is reciprocated in the bore. For simplicity, the usual piston rings for the piston 29 have been omitted from the drawing.

Connecting rod 28 is provided with a suitable bearing 30 engaging the crank pin 21, and fluid lubricant from crank case chamber 6 is supplied f thereto through a passage 32 and branch passages 33, by means of a reciprocating pump 35 which is operated by rotation of the crank shaft I5.

A suitable speed-responsive device is provided for controlling the outlet of fluid lubricant from passage 32 to vary the pressure of the uid lubricant therein as supplied from the pump 35, which device may comprise a. ball check valve 38, disposed in the inner portion of a bore 39, which extends radially inward from the outer peripheral surface of the counterbalancing portion 36 of the crank arm 26, the outer portion of the bore 39 being threaded to receive rstly, a threaded disc 4I, having an axial port 42 extending therethrough, and secondly, a screw plug 43, having an inner bore 44 into which the port 42 of the disc 4I opens. The screw plug 43 is provided with a laterally extending port 45 in the side wall thereof, which port connects the bore 44 with a branch passage 46, in the crank arm 26,'leading to passage 32, when the screw plug is tightly screwed into the bore 39.

The ball check valve 38 is designed to be of such weight that the centrifugal force acting thereon, uponA rotation of the crank shaft I5 above a predetermined speed, is sufiicient to cause the ball check valve to maintain the port 42 closed against the pressure of uid lubricant tending to unseat the ball valve and supplied from passage 32 through the branch passage 46, port 45, bore 44, and port 42. When the crank shaft I5 rotates at less than the predetermined speed, the pressure of the fluid lubricant supplied from passage 32 is suicient to unseat the ball check valve against the centrifugal force acting thereon, and fluid lubricant thus escapes past the ball check valve, through the. inner portion of the bore 39, and out into the crank case chamberv 6 through a port 41.

The pump 35 may comprise a tubular piston 48, having a longitudinal bore 49, which piston is pivotally connected at one end to a crank pin 5| secured in eccentric relation to the center of rotation of crank shaft I5 at the end of the crank pin 21 by screws 52, only one of which is shown. Upon rotation of the crank shaft I5, piston 48 is reciprocated within a chamber 53 of a piston cylinder 54, which is provided with a trunnion portion 55 pivotally mounted within a bearing member 56 secured to the crank case section 5, whereby angular movement of the piston cylinder 54 is permitted, in following the movement of the crank pin 5I.

Fluid lubricant from crank case chamber 6 is supplied to the piston chamber 53, at a point imniediately below the upper extremity of movement of the piston 48,5through a port or opening 51 in the bearing 56 and a passage 58 in the trunnion portion 5 5 connecting the piston chamber 53 and the port 51. A screen 59, which extends across the port 51, prevents the entrance of foreign particles into the piston chamber 53.

In accrda-nce `with one of the objects of my invention, I provide a bore 6I in the trunnion portion 55 of the piston cylinder 54, which bore connects passageA 58 to the space in crank case chamber 6 above the level of the fluid lubricant therein,l vand a choke plug 62 screwed 'into the outer enlarged threaded portion of the bore 6I, which plug is provided with a restricted port or passage63 therein, the purpose of which will be explained hereinafter.

Thebore 49 of the piston 48 communicates with'a' passag-e 32a in the crank pin 5I through a port64,the passage 32a being connected to the passage 32 in the crank pin 21. An inlet port 65, in' the opposite or lower end of the piston 48, connects the bore 49 with the piston chamber 53, and a ball check valve 66 disposed in the bore 49 of the piston is adapted to unseat to permit uid lubricant to pass from piston chamber 53 into the bore 49 through the port 65, and to reseat to close the port 65 and thereby prevent reflux of fluid lubricant from the bore 49. A pin 61, extending across the piston Within the bore 4 9, serves to limit the extent of the opening movement of the ball check valve 66.

The piston cylinder 54 is provided with a horizontally disposed cylindrical extension4 ,68 opposite the trunnion portion 55, which extension is provided with a chamber 69 opening into the crank case chamber 6. chamber 69 is a suitable pressure responsive device, such as the piston. 1I, having a continuous helical groove on the outer surface thereof adapted to receive fluid lubricant from the crank case chamber for lubricating and sealing purposes, which piston is provided with a stem 12 extending into the crank case chamber 6. Communication is established between the inner or confined portion of the chamber 69 of extension 68 and bore 49 of the piston 48, through a port 13 in the wall of piston cylinder 54 anda series of ports 14 in the wall of piston 48, the ports 14 being adapted to register successively with the' port 13 upon movement of the piston 48.

It will be apparent from the foregoing that upon rotation of the crank shaft I5, the upward stroke of pump piston 48 creates a vacuuml or partial vacuum in the piston chamber 53 whereby the static head of the fluid lubricant in the crank case chamber, as well as the air pressure acting down on the surface of the iluid lubricant in the crank case chamber, causes fluid lubricant to be supplied to the piston chamber vthrough screen 59, port 51, and passage 58, after the piston 48 uncovers the passage 58. At the same time, due to the higher pressure of the air' in the crank case chamber above the fluid lubricant therein relative to the partial vacuum in the piston chamber 53, a certain amount'of air is admitted to passage 58 through the choke plug 63 and enters the piston chamber 53 along with the fluid lubricant. The uid lubricant being supplied through passage 58 from the crank case chamber immediately closes up the port 6I and the air admitted through the choke plug is trapped in the fluid lubricant admitted to the piston chamber, so that instead of there being a homogeneous incompressible column of iluid lubricant in the piston chamber, there is a slightly compressible column comprising a mixture of air and fluid lubricant.

On the downward stroke of the piston 48, the piston closes the passage 58 upon initial movement and upon further movement exerts a, compressive force on the mixture of air and fluid Disposed within the lubricant trapped in the piston chamber 53 below will be hereinafter pointed out.

The compressive force exerted by pump piston `48 on the mixture of air and fluid lubricant in the piston chamber 53 causes the check valve 66 to unseat and'permit the mixture of air and fluid lubricant to ow therepast into the bore 49, whence upon successive downward strokes of the pump piston it is forced upwardly into passages 32a and 3,2. I have observed, incidently, that in some cases, a certain noise of operation of the pumpv piston may be reduced or eliminated by varying the distance of the limiting pin 61 from the ball check valve 63 to vary the extent of opening movement thereof.

If the crank shaft is rotating at less than the above mentioned predetermined speed there is no build-up of pressure in the 'fluid lubricant system due to the fact that the ball check valve 38 is unseated by the pressure of the fluid lubricant which escapes from passage 32 through branch passage 46, past the ball 'check valve 38,

and out at the port 41 into the crankl case chamber 6. On the other hand, if crank shaft I5 rotates at a speed higher than thepredetermined speed, ball check valve 38 closes as previously described, thus closing off the outlet of uid lubricant through port 41 and causing a build-up of fluid lubricant pressure in the bore 49 of the piston 48 and in the chamber 69 ofthe cylindrical extension 68, which pressure is sufficient to move the piston 1| and its stem 12 outwardly.

The end section 9, which is secured to the crank case section 5 by suitable screws or bolts 16, one of which is shown, is provided at its upper portion with a spout or opening 11 that communicates with the crank case chamber 6 through a passage 18 in the end wall of the crank case section 5, uid lubricant being poured therethrough into the crank case chamber 6.

Any suitable cap or cover may be provided for closing the opening 11 as, for example, the cap member 19, which is suitably hinged to the casing section 9 and provided with a spring clamp 8| for engaging a notch 92 in the casing 9 to maintain the cap member in closed position. The cap member 19 may also, as shown, be adapted to permit the release of pressure within the crank case chamber 6 andto prevent the inux of air or foreign particles into the crank case chamber by means of a check valve disc 83 slidably carried on a pin 84 secured to the cap member, check valve disc 83 Abeing adapted to seat upon an annular seat rib 85 surrounding the opening 11. The .valve disc A83 is unseated when the pressure within the crank case chamber 6 exceeds atmospheric pressure, equalization of pressure being eiected through an atmospheric port 86 in the cap member above the valve disc. Y

The lower portion of the end section 9 is provided with a threaded opening 81 through -which the level of. the ilud lubricant in the crank case section 6 may be determined, as well as drainage of the fluid lubricant from the crank case chamber effected, if so desired, a screw plug 88 being provided to close the opening 81.

In accordance with another object of my invention, I provide an unloading mechanism comprising the ball check valve 9|, disposed in a bore 92, which extends through the wall of the end casing section 9, and an operating lever 93 for the valve 9|, which lever is pivotally mounted at one end above the valve 9|, on a pin 94 secured to a lug 95 which is suitably attached to the inner surface of the wall of the casing section 9. the opposite end of the lever 93 being engaged by the end of the stem 12 of the piston 1|. A relatively stiff spring 9,6 is interposed between the lever 93 and the ball check valve 9|; one end of the spring being supported by a lug 91 on the the bore 92, so that the ball check valve 9| is moved into seated relation on a valve seat constituted by a tapered shoulder 98 in the bore 92, when the lever 93 is moved in a counterclockwise direction. A rigid member, such as the uted stem 96a, may be employed instead of the spring 96, as shown in Fig. 2.

Another spring |'9|, supported at one end in a recess |92 in the wall of the end casing section 9 and at the opposite end by a lug |93 on the lever 93, which lug is situated at a point between the lug 91 and the end of the lever 93 which engages I the stem 12 of the piston 1|, is provided for biasing the lever 93 in a clockwise direction whereby the lever is caused to rmly engage the end of the stem 12 for preventing a chattering noise at the point of contact. The spring |9| is not necessary for the operation of the compressor, it being desirable only as a means for reducing operating noise.

It should be noted that the spring 96 is of such length that when the lever 93 is in the position shown in Fig. l, the ball check valve 9| is unseated from the valve seat 98. This is because the spring 96 is so stii, that is, so highly tensioned, that appreciablevunseating movement of the check valve might not be permitted if the spring were to hold the valve on its seat.

The outer portion of the bore 92 is threaded to receive the end fitting of a pipe |94, the end f1tting on the opposite end of which .is threaded into the cuter portion of a bore 95 in the wall of the piston section 8, the bore E95 opening into the compression chamber portion of the bore 3l at a` point adjacent to the intake and discharge valve casing section i A ball check valve |96 is disposed in the bore |95 and is biased toward seating relation on a valve seat constituted by a tapered shoulder |01 in the bore |95, by a spring |98 in opposition to the pressure of fluid compressed in the compression chamber.

The casing section contains a cylindrical intake valve chamber into which an intake pipe 2 opens, and a cylindrical discharge valve chamber ||3 out of which leads a discharge pipe I4.

Any suitable intake valve and discharge valve mechanism may be provided in the casing section Il. The intake valve mechanism, shown for purposes of illustration, may comprise a valve seat disc l I5 having a plurality.7 of intake ports H6, extending axially therethrough, and a peripheral rib ||1. An annular valve disc ||8 is biased into seated relation on one face of the seat disc 5 to close the ports i! 6, by a spring ||9 which is interposed between the valve disc ||8 and a anged collar |29. The iianged collar |29 has a hub or central stem portion |2|, for securing the collar in spaced relation to the seat disc. 'I'he stem |2| passes through the central opening in the valve disc I9, and has a shoulder engaging one face of the seat disc, and a threaded portion extending through a central threaded opening or hole in the seat disc H5, which threaded portion is adapted to have a lock nut |22 screwed thereon into engagement with the opposite face of the seat disc. Axially extending passages |2|a in the stem |2| are provided to permit the flow of uid from the ports H6 through the central opening in the valve disc 8, when-the valve disc is unseated from the face of the seat disc H5, whereby a rapid flow of uid past the valve disc may be effected. Y

The assembled intake valve mechanism, is inivvcr and the other end being supportedvwithin serted as a unit, with the flanged collar |29 en- 75 tering rst, into a bore |23 extending through the casing section II and perpendicularly intersecting the intake valve chamber I I, thevalve mechanism being adapted to be supported on an annular shoulder |24, surrounding the bore |23 in the intake valve chamber I I I, which shoulder engages'the peripheral rib |I1 of the seat disc II5. The shoulder |24 is so positioned that when the valve mechanism is supported thereon, the lower face of the flanged collar is substantially flush with the inner surface of the casing section II. A screw plug |25, screwed into the outer portion of bore |23, is adapted to secure the valve mechanism within the bore |23, the plug being bored nd counterbored to provide a recess or chamber y|26 therein and an outer rim, which rim fits v a spring |39 interposed between the seat disc and closely around the seat disc ||5 and engages the peripheral rib |I1 to press it tightly in sealed relation against the shoulder |24. Recess |26 in the screw plug |25, communicates with the intake valve chamber III through a plurality of ports |21 in the outer rim of the screw plug.

A cap nut |28, screwed over the exposed threads of the screw plug |25, serves to lock the plug in position and in some measure to prevent unauthorized access to the valve mechanism.

The discharge Valve mechanism is similar in construction to the intake valve mechanism, just described, and may comprise a valve seat disc |35 having a plurality of discharge ports |36 therein and a peripheral rib |31, a valve disc |38 being biased into seated relation on one face of the valve seat disc |35 to close the ports |36, by

a flanged collar |40. The flanged collar is provided with a central stem or hub which passes through the central opening in the annular valve disc |38 and rests on theface of the seat disc |35, a stud bolt I4I, secured in a central threaded bore in the seat disc, being inserted through a central bore in the hub portion of the flanged collar ,|40 and being provided with suitable nuts |42 for securing the flanged collar to the seat disc |35.

' Axially extending passages I4|a in the hub portion of the flanged collar |40 provide a path for the ow of fluid from ports |36 through the central opening in the annular valve disc |38.

The discharge valve mechanism is inserted as a unit, with the seat disc |35 entering first, into a bore |43 extending through the casing section I I and perpendicularly intersecting the discharge valve chamber II3, the valve mechanism being adapted to be supported on an annular shoulder |44, surrounding the bore |43 in the discharge valve chamber |I3, which -shoulder engages the peripheral rib |31 of the seat disc |35. The shoulder |44 is so positioned that when the valve mechanism is supported thereon, the lower face of the valve seat disc |35 is substantially flush with the inner surface of the casing section II.

A screw plug |45, screwed into the outer portion of the bore |43, is adapted to secure the valve mechanism within the bore |43, the plug being' bored to provide a recess or chamber |46 therein and an outer rim, which rim fits closely around the seat disc |35 and engages the peripheral rib |31 to press it tightly in sealed relation against the shoulder |44. The recess |46 of the screw plug |45, into which the flanged collar |40 extends, communicates With the discharge valve chamber I|3 through a plurality of ports |41 in the outer rim of the screw plug.

A cap nut 48, similar to the cap nut |28, is screwed over the exposed threads of the screw plug |45.

Upon the suction or downward stroke of the compressor piston 29, fluid is drawn into the compression chamber above the piston 29 through the intake pipe ||2 and past the outer 'and inner edges of annular valve disc I I8, which is unseated against the tension force of the spring I I9 by the higher pressure in recess |26 and intake chamber III. Upon the compression or upward stroke of piston 29, valve disc ||8 is seated to prevent the reflux of iiuid therepast, and annular valve disc |38 of the discharge valve mechanism is unseated against the force of the spring |39, the compressed uid flowing past the outer and inner edges of the valve disc |38 and out through the discharge pipe I4.

In operation, assuming the partsof the compressor to be in the position shown in Fig. 1, uid compressed by the piston 29 within the compression chamber portion of bore 3|, will be forced past the ball check valve |06, through pipe |04, past the unloading ball check valve 9|, through crank case chamber 6, passage 18, opening 11,

past valve disc- 83 which unseats upon higher way of port 41 in the crank arm. When the ball` check valve 38 closes the port 42, the only escape for the fluid lubricant supplied to the passage 32 is through the' space between the engaging bearing surfaces of the crank pin 21 and the connecting rod bearing 30, which space is so restricted that continued operation of the pump 35 causes suicient pressure of fluid lubricant to be developed in the chamber 53 of pump piston 48 and in the chamber 69, that the piston 1I is moved to the right, as viewed in Fig. 1, toy move the operating lever 93 in a counterclockwise di@ rection. The ball check valve 9| is thus moved to seated position on its seat 98, to cut off the unloading communication to atmosphere, previously described, the tension developed by the compression of spring 96 being adequate to prevent opening movement of the. ball check valve 9|. The loading of the compressor is thus effected only after the compressor attains a predetermined speed of operation, fluid drawn into the compression chamber of the compressor on the suction or down stroke of piston 29 being discharged out through the discharge pipe I I4 upon compression or up stroke of the piston.

I have observed that in the operation of the compressor there is a tendency for the unloading ball check valve 9| to chatter on its valve seat, due to the fluctuation of fluid lubricant pressure, acting through the piston 1|, which causes the operating lever 93 to vibrate, thereby resulting in an undesirable noise of operation. The spring 96 is accordingly designed to be relatively stiil", that is, to have a relatively high tension, both in order to withstand the relatively high pressures acting thereon and in order that it will continue to maintain sufficient force on theA ball valve 9| to maintain it on its seat against the Cil |04, despite the vibration of the operating lever 93, whereby chattering of the valve 9| on its seat is prevented. Furthermore, the vibration of the lever 93 is reduced to a negligible degree due to the effect of the cushioning air admitted through choke plug 62 into the pump piston chamber 53. Since the cushioning air is commingled with the fluid lubricant forced into the bore 49 of the iiuted stem 96a does not act to bias the ball valve pump piston 48, incipient iluctuations in the pressure of the fluid lubricant in bore 49, which pressure acts continuously on piston 1| through the ports 14 and port 13, are effective to compress this commingled air rather than to cause movement of the piston 1|. Thus the tendency for the fluid pressure acting on piston 1| to fluctuate during the operation of the pump while the compressor is operating in a loaded condition is greatly reduced and the result is that the iluid lubricant, through piston 1|, continues to exert a substantially constant pressure on the lever 93, so that vibrational movement of the lever 93 is reduced to a negligible degree if not entirely eliminated. The choke plug 62 thus serves to effect substantial elimination of the vibration of the unloading valve operating lever 93 as well as to effect cushioning of the pump piston 4B.

In the embodiment of my invention shown in Fig. 1, the spring 96 may be sufficiently effective to prevent chattering of the ball valve 9| on its seat without the` eiect of the choke plug 62, but

in the embodiment shown in Fig. 2, there may be a chattering of the valve 9| on its seat, unless the choke plug 62 is employed, since the rigid 9| on its seat, as does the spring 96, and variations in the pressure of fluid lubricantfapplied through piston 1| to lever 93 will be sufficient to permit slight unseating movements of the ball valve. The choke plug 62 is thus of special utility where a rigid member, such as the iluted stem 96a, is employed, since it prevents such variation in the force applied to the lever 93 by the fluid lubricant, through piston 1|, as would permit the ball valve 9| to unseat slightly and cause a chattering noise.

If, for any reason, such as in stopping the compressor or as a result of the attained pressure against which the compressor works, the speed of operation of the compressor is reduced below the above mentioned predetermined speed, the speed-responsive ball check valve 38 is unseated and uid lubricant from passage 32 ows out through port 4-2, vpast the ball check valve 39, through port 41, into the crank chamber 6. The pressure of the fluid lubricant in bore |39 of the pump piston 48 and in chamber 69 acting on the piston 1| is thus reduced, and spring |01 is effective to return the piston 1| to the vposition shown in Fig. 1, the operating lever 93 being moved in a clockwise direction. 'I'he tension of spring 96 maintaining the ball check valve 9 |v on its seat 99, is thus released and, .as a result, the pressure of the uid compressed by the compressor and supplied through pipe V|ll4 is effective to blow or unseat the valve 9| from its seat.

The communication, previously described, between the compression chamber and atmosphere past the unlo` 'ng valve 9|, is thus established and the comp,I ssor is thereby unloaded.

If, while the compressor is operating in a loaded condition,the spring 96 fails or breaks, the unloading valve 9| is blown from its seat by the pressure of the uid compressed by'the compressor and supplied through the pipe |04. 'I'he unloading of the ,compressor will thus attract the he may take immediate steps to remedy it. If the spring |6| fails or breaks while the compressor is operating either in a loaded or unloaded condition, the operating condition remains unchanged and the compressor continues to operate. In such case, there arises-only the objectionable noise occasioned by the chattering of the operating lever 93 against the end of the stem 12 of the piston 1|. If the spring |0| has broken or failed during the operation of the compressor while loaded, and the speed of operation of the compressor is subsequently reduced below the predetermined speed above mentioned, the tension of spring 96 acts to move the lever 93 in a clockwise direction, so that the. tension of spring 96 is released and as a result the ball valve 9|- is Ablovvn from its seat and the compressor unloaded.

In the case of the flutedv stem 96a being employed in the above instance, the release of pressure exerted by fluid lubricant, through piston '1| on the lower end of the lever 93, permits the ball valve 9| to be blown from its seat to unload the compressor.

It will thus be apparent that due to the arrangement of the unloading valve and its operating lever which I have devised, movement of the unloading valve 9| to open or unloading position is not under the control of spring pressure, spring |01 being employed merely for maintaining the engagement of the operating lever with the end of the piston stem 12 to prevent chattermechanism.

While I have illustrated and described but two embodiments of my invention, in connection with a single stage compressor, it will be understood that my invention is equally adaptable to a multistage compressor and that various omissions, additions, or changes may be made therein without departing from the spirit thereof. It is not my intention, therefore, to limit the scope of my invention except as required by the prior art and as defined in the appended claims.

Having now described my invention, what I claim as new and desire to secure by Letters Patent, is:

1. A control mechanism for a iiuid compressor, comprising valve means operable to effect loading and unloading of the compressor, an operating lever for said valve means, said lever being pivoted at one, end and engaging the said valve means at an intermediate point on the lever, and fluid pressure actuated means controlled by the speed of operation of the compressor and adapted to engage the other end of the lever for moving the :lever to operate said valve means to effect loading of the compressor, said valve means being so constructed and arranged as to be subject to the pressure of uid compressed by the compressor and operated thereby to effect unloading of the compressor.

2. A control mechanism for a fluid compressor, comprising a valve operable into one position for `eiecting the loading of the compressor and out of said position for effecting the unloading of the,

compressor, an operating lever for said valve pivoted at one end, fluid pressure actuated means controlled by the speed of operation of the compressor for engaging the other end of said lever to move it about the pivoted end, an'd means interposed between said valve and said lever at a point on the lever intermediate the ends thereof, whereby movement of the lever occasioned as a result of actuation of the fluid pressure actuated means is effective to move the said valve into 4the said one position to effect loading of the compressor.

3. A control mechanism for a fluid compressor, comprising a valve operable into one position for effecting the loading of the compressor and out of said position for effecting the unloading of the compressor, an operating lever for said valve pivoted at one end, fluid pressure actuated means controlled by the speed of operation of the compressor for engaging the other end of said lever to move it about the pivoted end, and resilient means interposed between said valve and sai'd lever at a point on the lever intermediate the ends thereof, whereby movement of the lever occasioned as a result of actuation of the fluid pressure actuated means is effective to move the said valve into the said one position to effect loading of the compressor, said resilient means being adapted to compensate for vibratory movements in said lever and maintain said valve in the said one position when said fluid pressure actuated means is actuated.

4. A control mechanism for a fluid compressor, comprising valve means operable to effect loading and unloading of the compressor, an operating lever for said valve means pivoted at one end, and engaging said valve means at an intermediate point on said lever, uid pressure actuated means adapted to operatively engage the opposite end of said lever for moving it to operateV said valve means to effect loading of the compressor, means responsive to the speed of operation of the compressor for effecting the actuation of said fluid pressure actuated means when the speed of operation of the compressor exceeds a predetermined speed, said valve means being so constructed and arranged as to be subject to the pressure of fluid compressed by the compressor and operated by such fluid under pressure to effect the unloading of the compressor when the speed of operationl of the compressor reduces below said predetermined speed.

5. The combination in a uid compressor having a crank shaft, a pump operated by the crank shaft for supplying fluid lubricant under pressure to the bearings of the compressor, and a control mechanism for said compressor including a valve adapted to seat on a cooperating valve seat to close a communication through which said compressor is unloaded, an operating lever for said valve adapted to move said valve into seating relation on its valve seat in response to a variation in the pressure of the fluid lubricant supplied by said pump to the bearings of the compressor, of means for reducing the vibra-v tional movement of said operating lever, caused by operational fluctuations in the pressure of the fluid lubricant supplied by said pump and resulting in a chattering of said valve on its seat, said means comprising a passage for admitting air along with fluid lubricant into said pump.

6. The combination in a fluid compressor comprising a casing having a crank case chamber, a crank shaft, a pump operated by the crank shaft for supplying iiuid lubricant under pressure to the bearings of the compressor, and al control mechanism for said compressor including a valve adapted to seat on a cooperating valve seat to close a communication through which' said'compressor is unloaded, an operating lever for said valve adapted to move said valve into seating relation on its valve seat in response to a variation in the pressure of the fluid lubricant supplied by said pump to the bearings of the compressor, of means for reducing the vibrational movement of said operating lever, caused by operational fluctuations in the pressure of the fluid lubricant supplied by said pump and resulting in a chattering of -said valve on its seat, said means comprising a passage for admitting air from said crank case chamber along with fluid lubricant into said pump. l 7. The combination in a uid compressor com-l prising a casing having a crank case chamber, a crank shaft rotatable in said crank case chamber, a pump operated by said crank shaft for supplying fluid lubricant from the said crank case chamber to bearings of the compressor, a valve adapted to engage a valve seat to close a communication through which the compressor is unloaded, an operating lever for effecting movement of said valve into engagement with its seat, and pressure responsive means actuated by Variations in the pressure of the fluid lubricant supplied by said pump, for moving said lever to cause said valve to engage its seat, of means for reducing the vibration of said valve operating lever occasioned by operational uctuations in the pressure of the fluid lubricant supplied by said pump whereby to prevent chattering of said valve on its seat, including means for admitting air into said pump, along with fluid lubricant, whereby the pressure acting on said pressure responsive means is rendered substantially constant.

8. The combination with a iluid compressor having an operating shaft, and a pump operated byoperation of said shaft for circulating liquid under pressure, of a valve controlled by the Vto vibrate said valve.

9. The combination with a fluid compressor having an operating shaft, a pump operated by operation of said shaft for circulating liquid under pressure, of a valve operable to load and unload the compressor, a lever for operating said valve, means responsive to variations in the pressure of the circulating liquid for moving said lever to operate said valve, and means for introducing quantities of gas into the circulating liquid for minimizing operational fluctuations in the pressure of the circulating liquid and thereby reducing vibratory movement of said lever.

10. The combination with a fluid compressor having a crank chamber containing fluid lubricant, and a crank shaft in said chamber, of a reciprocating pump operated by rotation of said crank shaft for supplying uid lubricant from the crank chamber to moving parts of the compressor and having an intake passage extending below the level of the fluid lubricant inthe crank chamber, a valve controlled by the opposing forces exerted by the pressure of uid compressed by the compressor and by the pressure of the uid lubricant supplied by said pump and operative to load or unload the compressor dependent on the fluid lubricant pressure, and a passage establishing communication between the space above the uid lubricant in the crank chamber and the said intake passage for said pump, through which passage a gas is introduced into the fluid lubricant supplied by said pump for minimizing operational fluctuations in the uid 10 lubricant pressure tending to vibrate said valve..

11. A control mechanism for a fluid compressor, comprising a valve effective when in one position to cause loading of the compressor and when out of said one position to cause unloading of the compressor, a lever for moving said valve, said lever being pivoted at one end and cooperating with the said valve at a point intermediate the ends of the lever, fluid pressure responsive means actuated upon an increase in the pressure of fluid acting thereon for moving the other end of the lever` pivotally about the said one end to move the said valve into and hold it in the said one position to cause loading of the compressor, and means for causing the pressure of the fluid acting on said fluid pressure responsive means to exceed the said certain pressure only when the compressor operates at a speed in excess of a certain speed.

I2. A control mechanism for a fluid compressor, comprising a valve controlling a communication through Which fluid under pressure is vented to unload the compressor, a valve seat for said valve, said valve being effective When seated on the valve seat to close the communication and thereby to cause the compressor to be loaded, and When unseated from the valve seat to open the communication and thereby to cause the compressor to be unloaded, a lever for moving said valve into seated relation on the valve seat, said lever being pivoted at one end and cooperating With the valve at a point intermediate the ends of the lever, fluid pressure actuated means effective upon an increase in fluid pressure acting thereon to pivotally move the other end of the lever so that the lever moves the valve toward and into seated relation onthe valve seat, and means for 'controlling the pressure of the fluid acting on the fluid pressure actuated means dependent upon thespeed of operation of the compressor.

13. A control mechanism for a fluid compressor, comprising a valve controlling a communication through which fluid under pressure is vented to unload the compressor, a valve seat for said valve, said valve being effective When seated on the valve scatto close the communication and thereby to cause the compressor to be loaded, and when unseated from the valve seat to open the communication and thereby to cause the compressor to be unloaded, a lever for moving said valve into seated relation on the valve seat, said lever being pivoted at one end and cooperating Withv the valve at a point intermediate the ends of the lever, uid pressure actuated means effective upon an increase in uid pressure acting thereon to pivotally move the other end of lthe lever so that the lever moves the valve toward and into seated relation on the valve seat, and means for controlling the pressule of the fluid acting on the fluid pressure actuated means dependent upon the speed of operation of the compressor, the pressure of the fluid acting on the fluid pressure actuated means being eifective through said lever to hold said valve in seated relation on the valve seat against the pressure of the uid in the communication, .and the pressure of the uid in the communication being effective to unseat the valve and thereby unload the compressor when the pressure of the fluid acting on the fluid pressure actuated means de- 5 creases sufficiently.

14. The combinationlvvith a compressor having a casing embodying a compression chamber and a crank-case chamber, the crank-case chamber being in communication with the atmosphere, of 10 an unloading communication connecting the compression chamber to the crank-case chamber,

a valve controlling said communication, an operating lever for said valve pivoted at one end thereof on the casing and Within the crank-case 15 chamber, and uid pressure responsive means within the crank-case chamber actuated, according to the speed of operation of the compressor, for moving the opposite end of the lever in one direction, said valve being moved by said lever 20 upon movement thereof in the said one direction,

to close said communication and thereby effect loading of the compressor.

15. A control mechanism for a fluid compressor, comprising a pump for supplying fluid lubri- 25 cant under pressure to parts of the compressor,

a valve effective When in one position to cause loading of the compressor and when out of said one position to cause unloading of the compressor, said valve being subject to the pressure of 30 fluid compressed by the compressor and tending to shift said 'valve out of said one position, and means actuated by the pressure of fluid lubricant supplied by said pump for shifting the said valve into and holding said valve in said one position 35 against the opposing pressure of the fluid cornpressed by the compressor as long as the pressure of the fluid lubricant exceeds a certain pressure, and means for preventing the pressure of fluid lubricant, as supplied by said pump, from exceedto ing said certain pressure as long as the speed of the compressor is below a certain speed.

16. A fiuid compressor unloading mechanism comprising, in combination, a pump for supplying uid lubricant under pressure to parts of the 45 compressor, means controlled by thespeed of the compressor and operative to cause an increase in pressure of the fluid lubricant as supplied from said pump, a valve subject to the pressure of uid compressed by the compressor and shifted there- 50 by to an open position for establishing a communication through which iuid under pressure is released from a compression chamber of the compressor to atmosphere and the compressor thereby unloaded, and means for exerting a force 55 on the said valve proportional to the lubricant pressure in opposition to the force of the uid compressed by the compressor, said valve being shifted by the last said means to a closed position to prevent the release of iiuid under pres- 60 sure from the compression chamber of the compressor through said communication and thereby to cause loading of the compressor when the pressure of the fluid lubricant exceeds a certain uniform pressure. 65

1'7. A fluid compressor unloading mechanism comprising, in combination, a pump for supplying fluid lubricant under pressure to parts of the compressor, means responsive to the speed of operation of the compressor for causing the pres- 70 sure of the fluid lubricant, as supplied byv said pump, to increase above a certain uniform pres-` sure only when the speed of operation of the compressor exceeds a certain uniform speed, a valve subject to the pressure of uid in a com- 75 pression chamber of the compressor arid actuated by the pressure of such iluid to open a communication through which the fluid under pressure is released from the compression chamber to atmospnere to unload the compressor, and means for causing the pressure of the fluid lubricant to be exerted on said valve in opposition to the pressure of the fluid compressed by the compressor, said valve being shifted yto and held in closed position to prevent the release of fluid under pressure from the compression chamber of the compressor through said communication to thereby effect loading of the compressor only when the pressure of the fluid lubricant is above said certain uniform pressure'.

18. A fluid compressor unloading mechanism comprising, in combination, a pump for supplying fluid lubricant under pressure to parts of the compressor, means responsive to the speed of operation of the compressor for causing the pressure of the fluid lubricant, as supplied by said pump to increase above a certain pressure only when the speed of operation of the compressor exceeds a certain speed, a valve so constructed and arranged that it is urged in one direction by the pressure of fluid compressed by the compressor to establish a communication through which fluid under pressure is released from a compression chamber of the compressor to atmosphere to thereby cause unloading ofthe compressor, and means for causing the pressure of the fluid lubricant to exert a force on the said pressor, means operative'automatically when the t speed of the compressor exceeds a certain uniform speed for causing the pressure of the iiuid lubricant, as supplied by said pump, to increase above a certain pressure, a valve subject to thev pressure of fluid in a compression chamber of the compressor and unseated thereby to establish a communication through which fluid under pressure is released from the compression chamber to atmosphere to cause unloading of the compressor, and means including a movable abutment subject to the pressure of the fluid lubricant and a lever actuated thereby for applying a force to the said valve in opposition to the fluid pressure inthe compression chamber and acting on said valve for causing the said valve to be held seated and thereby cause loading of the compressor when the pressure of the fluid lubricant exceeds said certain pressure.

PHILIP L. CRITTENDEN.

CERTIFICATE OF CORRECTION Patent No 2,110 ,720.

March 8, 1958 PHILIP L. CRITTENDEN.

It is hereby certified that error vappears in the printed specification of the above numberedpatent requiring correction as follows: Page 7, first column, line 20, claim.ll, after "thereon" insert the words to at least a certain pressure; and that the said Letters Patent Yshould be read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 27th day of September, A'. D.'

lSeal) Henry Van Arsdale Acting Commissioner of Patents. 

